Question: Tiffany is 8 years younger than Brandon. Nine years ago, Brandon was 3 times as old as Tiffany. How old is Brandon now?
We can use the given information to write down two equations that describe the ages of Brandon and Tiffany. Let Brandon's current age be $b$ and Tiffany's current age be $t$ The information in the first sentence can be expressed in the following equation: $b = t + 8$ Nine years ago, Brandon was $b - 9$ years old, and Tiffany was $t - 9$ years old. The information in the second sentence can be expressed in the following equation: $b - 9 = 3(t - 9)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $b$ , it might be easiest to solve our first equation for $t$ and substitute it into our second equation. Solving our first equation for $t$ , we get: $t = b - 8$ . Substituting this into our second equation, we get the equation: $b - 9 = 3($ $(b - 8)$ $ -$ $ 9)$ which combines the information about $b$ from both of our original equations. Simplifying the right side of this equation, we get: $b - 9 = 3b - 51$ Solving for $b$ , we get: $2 b = 42$ $b = 21$.